1. Field of the Invention
The invention relates to stabilizers for inorganic silicate corrosion inhibitors used in antifreeze/coolant formulations and particularly relates to such stabilizers which are organic polysiloxanes.
2. Related Stabilizers in the Field
Antifreeze compositions containing glycols and various corrosion inhibitors are well known in the prior art as is illustrated by U.S. Pat. Nos. 3,282,846 and 3,362,910. The use of the relatively inexpensive and effective borax and silicates in glycol formulations as corrosion inhibitors is well illustrated by these patents. It is conventional in this art to make a glycol concentrate which is then sold to end users for use as a coolant in automotive radiators and the like after dilution with water.
In the past, it has been found that glycol concentrates prepared using conventional corrosion inhibitors such as borax and silicates had a tendency to develop irreversible silicate gels upon standing for a period of time in a warehouse or store. The end user, when he attempted to pour the glycol concentrate into his automotive radiator, found that the concentrate had developed "slugs" or gels which either did not pour readily or which tumbled out in discrete masses along with the liquid. The present invention was developed to eliminate this gel formation.
In U.S. Pat. No. 4,149,985, there is disclosed that a gellation resistant glycol composition containing borate and silicate additives can be made wherein the order of addition of the additives and the pH of the solution is closely controlled in order to obtain the gellation resistant formulation.
In U.S. Pat. No. 3,312,622, there is disclosed a corrosion resistant glycol composition containing an organosilicon co-polymer having carboxylate salt groups and silicate groups.
Other organosiloxane compounds are known to help prevent the silicates from forming gels. See, for example, the compounds disclosed in U.S. Pat. Nos. 3,337,496 and 3,341,469. The problem with the organosiloxane compounds of these patents is that relatively large quantities are required before effective stabilization is achieved. Particularly pertinent to the present invention are the ether modified polymethyl oxygen-containing silicone polymers of U.S. Pat. No. 4,287,077 which are also taught as being good gellation resistant additives. Unfortunately, the organosiloxane materials of U.S. Pat. No. 4,287,077 must be synthesized using expensive platinum catalysts. A simpler, less expensive method of preparation is desired.
Many types of organosiloxane compounds are known in the art. For example, U.S. Pat. No. 2,846,458 describes organosiloxane compounds that have been modified with ethers, particularly the mono- and diethers of glycols and polyglycols. Such materials were then known to be useful as surface-active agents, release agents, lubricants, antifoam agents and as cosmetic additives. These compositions did not encompass polymers of silicon.
A method for making carbalkoxyalkyl polysiloxanes is revealed in U.S. Pat. No. 3,065,202. Such compounds were useful as plasticizers for organopolysiloxane resins and rubbers and as lubricants. U.S. Pat. No. 3,105,061 teaches a method for the preparation of diorganopolysiloxane polymers by the reaction of diacyloxysilanes and siloxanes with mono- and dihydroxy silanes and siloxanes.
The addition of SiH compounds to aliphatic unsaturated compounds in contact with chloroplatinic acid can be achieved in the presence of hydroxyl compounds such as water or alcohols according to U.S. Pat. No. 3,398,174. The organosilicon compounds made therein may contain either substituents.
Finally, various organosiloxane compounds having cyano-, ether, hydroxy- or phenylorgano modifying moieties are taught in U.S. Pat. No. 4,331,555 which teaches that such compounds are useful as foam stabilizers in flexible polyester polyurethane foam.
There remains a need for a gellation resistant stabilizer that allows smaller effective amounts to be used and which is less expensive than those currently used.